diff options
| author | Dmitry V. Levin <ldv@altlinux.org> | 2020-06-02 21:00:51 +0300 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2020-06-29 20:07:48 -0400 |
| commit | 52a238a13ae0edd4d510e84da5ad68d40b74d249 (patch) | |
| tree | a8331878ec4fbb61b0ad6c5ec200e529705660e6 /arch | |
| parent | ddb4a7b3a08a9a2867d9ca9d22f12d28e72b5075 (diff) | |
s390: fix syscall_get_error for compat processes
commit b3583fca5fb654af2cfc1c08259abb9728272538 upstream.
If both the tracer and the tracee are compat processes, and gprs[2]
is assigned a value by __poke_user_compat, then the higher 32 bits
of gprs[2] are cleared, IS_ERR_VALUE() always returns false, and
syscall_get_error() always returns 0.
Fix the implementation by sign-extending the value for compat processes
the same way as x86 implementation does.
The bug was exposed to user space by commit 201766a20e30f ("ptrace: add
PTRACE_GET_SYSCALL_INFO request") and detected by strace test suite.
This change fixes strace syscall tampering on s390.
Link: https://lkml.kernel.org/r/20200602180051.GA2427@altlinux.org
Fixes: 753c4dd6a2fa2 ("[S390] ptrace changes")
Cc: Elvira Khabirova <lineprinter@altlinux.org>
Cc: stable@vger.kernel.org # v2.6.28+
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/include/asm/syscall.h | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h index 6bc941be6921..166fbd74e316 100644 --- a/arch/s390/include/asm/syscall.h +++ b/arch/s390/include/asm/syscall.h @@ -41,7 +41,17 @@ static inline void syscall_rollback(struct task_struct *task, static inline long syscall_get_error(struct task_struct *task, struct pt_regs *regs) { - return IS_ERR_VALUE(regs->gprs[2]) ? regs->gprs[2] : 0; + unsigned long error = regs->gprs[2]; +#ifdef CONFIG_COMPAT + if (test_tsk_thread_flag(task, TIF_31BIT)) { + /* + * Sign-extend the value so (int)-EFOO becomes (long)-EFOO + * and will match correctly in comparisons. + */ + error = (long)(int)error; + } +#endif + return IS_ERR_VALUE(error) ? error : 0; } static inline long syscall_get_return_value(struct task_struct *task, |